Content, such as digital data, is comprised of bytes of information, with each byte representing, in some sense, a sample of source data at a particular point in time and/or space. There is usually some type of redundancy in such data. As is well known, this fact is used to compress the data to make it more efficient for data transmission and storage.
In addition to data redundancy, data importance is another factor present in such data. In other words, some parts of the data are more important than others, from the point of view of human perception of the data.
One type of content is digital images. Digital images are comprised of pixels, with each pixel represented by one or more bytes of information. For typical color images, 3 color components (usually Red, Green and Blue) are needed, with each component typically represented by one byte of information. Hence, color images can be adequately represented by 3 bytes of information for every pixel in the image.
The number of pixels in an image is determined by the resolution of the image. A 1-MegaPixel image contains one million pixels. The amount of information carried by a 1-Mega Pixel color image is, therefore, of the order of 3 Megabytes. Today's digital cameras generate images much higher in resolution. A 6-Mega Pixel color image would translate to about 18 MB of data.
Since digital images carry so much information and take up lots of space, it is only natural that techniques are developed to compress the large of amount of image data. There are several image compression techniques that have evolved over time. Some of the popular standardized image compression standards are GIF, JPEG and JPEG2000. JPEG, for example, is able to compress a typical high resolution digital camera image to a ratio of 1:8 to 1:12, depending on the image content. Thus, instead of requiring 18 MB for a 6-Mega Pixel image, the compressed image requires a space of about 1.5-2.5 MB.
However, it is desirable to provide some pre-processing and post-processing that can provide further compression to a piece of content on top of that provided by the typical image compression standards and it is to this end that the invention is directed.